This invention is in the field of apparatus for installing pavement, especially concrete slabs as found, e.g., in roadways, sidewalks, patios, etc. More specifically, this invention relates to tools and apparatus for installing expansion joints in such pavement.
Joints and jointing materials are indispensible in applications where concrete, mortar, and the like are employed. Concrete and mortar expand or contract with temperature changes, and the dimensional differences which result from temperature changes in many parts of the country lead to enormous stresses in the concrete of mortar. These stresses cause random cracking. The resultant influx of water, freezing, expansion, and further stress leads to additional cracking of the concrete or mortar and its eventual disintegration.
One way to moderate the cracking problem is to provide joints in the paving, weak spots along which the cracking preferentially occurs. However, soil and water then penetrate the joints, leading to unwanted further cracking. Thus, it has become a preferred practice to insert an expansion-absorbing material into such pavement joints. A number of materials have been proposed for this purpose over the years; e.g., a composite which includes an asphaltic or rubber binder together with a fibrous filler is often employed. This and similar expansion material is available in about 10 ft. lengths, often about 1/4-1/2 in. thick, and 31/2-4 in. wide, especially adapted for sidewalks. Expansion material with other dimensions in available for different applications, such as highways.
When such expansion material is used in building concrete pavement it must be held in place along the desired joint line by some means until the concrete is poured on either side of it. This is not an easy task, because the expansion material is quite flexible, which makes it difficult to create a straight joint, especially a straight joint in which the expansion material is held at the correct height. Various tools and techniques for solving these problems have been described.
For example, U.S. Pat. No. 1,629,544 discloses apparatus for holding such expansion material in place while the concrete is poured on either side of it. U.S. Pat. Nos. 1,588,717 and 1,891,897 describe tools, crowning devices, which hold such expansion material in place. The tools described in each of the aforesaid patents are removable after the concrete is poured.
The prior art also discloses several complete expansion joints wherein a removable portion, in the nature of a crown cover for the expansion material, is disclosed. The following U.S. Patents are relevant in this regard: 2,189,437; 3,782,846; and 4,346,542.
However, none of complete joints described in the prior art and none of the tools designed to hold a joint expansion material is practical and economical. They are not adjustable for expansion joints of different lengths. Furthermore, the joints and tools of the prior art do not provide mechanism which permits proper alignment and location of the expansion material with respect to forms in which the concrete typically is poured. It is to these deficiencies in the masonry tools of the prior art that this invention is directed.
Thus, it is one objective of this invention to provide an expansion material-holding tool which can be removed from the concrete before it is set for reuse in the same pour.
It is a further objective of this invention to provide a tool whose length can be adjusted to accommodate various lengths of expansion material to permit, for example, the same tool to be used in pouring concrete sidewalks of different widths.
A still further objective of this invention is to provide a tool which permits the expansion material to be easily located and aligned in the forms commonly employed in concrete work.